Beverages such as beer and soft drinks are frequently packaged in cans which are marketed to consumers in groups termed "multipacks." Groups of six, eight or twelve cans, termed "six packs," "eight packs" and "twelve packs" respectively, are widely used for retail sales, with the six pack being the most popular. Six packs are typically shipped from the producer to the retailer in open-topped, low-sided corrugated cardboard cartons, four six-packs to a carton. The carton of six packs is often wrapped with a plastic shrink wrap to hold the six packs in place.
The six cans of a six pack are typically held together to form a rectangular two-row by three-column array with a flexible plastic holder termed a "top grip" which has loops into which the tops of the cans fit. The top grip generally maintains a separation of a few millimeters or so between the top portions of adjacent cans in the six pack.
Although the top grip generally maintains a separation between the top portions of adjacent cans in a six pack, the flexibility of the top grip permits adjacent cans to touch near the bottom of the cans. Touching of adjacent cans gives rise to serious problems in the shipment of six packs of cans. Motion during shipment often causes adjacent cans which are touching to rub one another at the points of contact. Such rubbing can wear away the graphics or labelling on the can. The resulting worn spots on the cans are unsightly and reduce the appeal of the product to potential customers. Moreover, adjacent cans which touch can rub one another to such an extent during shipment that a wall of one of the cans wears completely through. When the wall of a can wears through, liquid in the can leaks out. Even a single can which leaks in a shipment of cans of beverage represents a serious loss, since health codes frequently require that an entire shipment be scrapped if a single can leaks.
A further disadvantage of corrugated cardboard cartons for shipping six packs of cans is that moisture--from condensation, leakage, or other source--tends to weaken the carton. In humid climates, moisture from condensation can weaken a corrugated cardboard carton to such an extent that the carton cannot bear the weight of the cans being transported in the carton.
U.S. Pat. No. 3,650,395 to Hobbs discloses a tray formed with a number of depressions for locating the ends of containers such as cans or bottles. The tray is imperforate and is vacuum-formed from a thin sheet of synthetic plastic material. The edge of the tray has a continuous upstanding peripheral flange having at its upper edge an outwardly-projecting lip. To form a package, containers are placed in the tray with the bottom ends of the containers placed in the depressions of the tray. A film of synthetic plastic wrapping material is wrapped around the containers and the tray and heat shrunk to hold the containers and the tray together.
The tray of the '395 patent has a number of drawbacks, particularly with respect to its use in a high-speed commercial canning or bottling operation. For example, if a number of the trays are stacked one atop the other, adjacent trays tend to nest together and bind. Such binding tends to give rise to troublesome problems when stacks of trays are used to feed a high-speed can or bottle packaging machine. Moreover, in warehousing cartons of cans or bottles, warehouse operators frequently stack the cartons in multilayered structures in which--for stability--adjacent layers of cartons are oriented perpendicular to one another. The arrangement of such multilayered structures is called cross-stacking The outwardly-projecting lip of the peripheral flange of the tray of the '395 patent tends to interfere with cross-stacking shrink-wrapped packages of cans or bottles in the trays. In addition, canning and bottling operations are frequently high-volume, low-profit-margin businesses for which packaging costs represent a significant expense. Any reduction in the cost of a tray used in packaging cans or bottles would therefore be desirable.
U.S. Pat. No. 4,194,678 to Jasper discloses a shipping carton for bottles of medical liquids such as intravenous solutions. The carton is evidently made of corrugated cardboard and includes a reinforcing panel to form a rigid crush-resistent structure. A pocketed insert formed to accommodate the shape of the bases of the bottles is held in the bottom of the carton by the reinforcing panel. The pocketed insert can be a vacuum formed sheet with pockets which accommodate half or quarter portions of the bases of the bottles. The rigid shipping carton of the '678 patent is evidently subject to the drawbacks of corrugated cardboard containers noted above. Moreover, the shipping carton is unduly bulky and expensive for shipping beverages or other canned or bottled retail goods.
One of us invented a spacer tray for packaging cans or other containers which is the subject of U.S. patent application Ser. No. 16,310, filed Feb. 19, 1987. The particular embodiments of the spacer tray exemplified in the '310 application are formed of a plastic sheet material and are shaped to provide a plurality of receptacles to receive at least parts of bottom portions of containers. A particular embodiment of the spacer tray includes a plurality of openings passing through it which permit guide pins from a high-speed loading machine to project through the openings for locating the spacer trays and guiding bottom portions of containers into the receptacles during loading of the tray. Although the particular embodiments of the spacer trays exemplified in the '310 application satisfactorily solved problems of the prior art and are suitable for many packaging applications, there is room for improvement. Suitable openings for guide pins in such spacer trays can be provided; however, an additional manufacturing step and additional handling of the spacer trays during manufacture is required, which adds to the cost of the trays. In addition, because of the flexibility of such spacer trays, it is difficult to provide economically openings for guide pins with the desired dimensional stability for use with high-speed loading machines.